Orderly-micro-grooved pcd grinding wheel for positive rake angle processing and method for making same

ABSTRACT

Disclosed are an orderly-micro-grooved PCD grinding wheel for positive rake angle processing and a preparation method thereof. A PCD film is deposited on the outer circumferential surface of a wheel hub, and a plurality of microgrooves with high depth-width ratio and micro-grinding units with positive rake angles are orderly provided on the outer circumferential surface of the entire PCD film. The method includes: depositing the PCD film on the outer circumferential surface of the wheel hub by a HFCVD technique; and manufacturing a plurality of microgrooves with a high depth-width ratio (circumferential width: dozens of micrometers; depth: hundreds of micrometers) and an axial length that is equal to the thickness of the grinding wheel and a plurality of micro-grinding units with positive rake angles on the outer circumferential surface of the entire PCD film by water-jet guided laser technique, where the micro-grinding units and the microgrooves are orderly arranged.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationPCT/CN2019/090698, filed on Jun. 11, 2019, which claims the benefit ofpriority from Chinese Patent Application No. 201810608183.3, filed onJun. 13, 2018. The content of the aforementioned application, includingany intervening amendments thereto, is incorporated herein by reference.

TECHNICAL FIELD

This application relates to a grinding wheel and a preparation methodthereof, and more specifically to an orderly-micro-grooved PCD grindingwheel for positive rake angle processing and a method for making thesame.

BACKGROUND OF THE INVENTION

Grinding has been widely applied in the precision machining due to thecharacteristics of high processing precision and good surface quality.However, in the traditional grinding process, abrasive grains areirregularly arranged on the working surface of the grinding wheel, andvary in geometrical shape and size, so that the abrasive grains oftencut the surface of the workpiece in a large negative rake angle duringthe grinding process, which will increase the grinding force ratio,accelerate the conversion of grinding energy into heat and raise thegrinding temperature, affecting the surface quality and grindingefficiency. In addition, the grinding wheel also has disadvantages ofsmall chip space and low protrusion of abrasive grains, and the grainsare easy to fall off, which may easily cause a blockage at the grindingwheel and produce a local high temperature to damage the workpiecesurface, and reduce the service life of the grinding wheel.

Extensive researches have been performed to find a method for improvingthe grinding efficiency and service life of the grinding wheel. ChinesePublication No. 107962510A, titled “CVD diamond grinding wheel withordered surface micro-structure” put forward a method in which a diamondfilm is deposited on the outer circumferential surface of a grindingwheel hub by chemical vapor deposition, and a large number of staggeredand ordered microgrooves and grinding units with waist-type top surfaceare provided on the outer circumferential surface of the whole diamondfilm by pulsed laser beam. This method improves the removal rate andgrinding efficiency of the surface material and increases the holdingforce of the grinding wheel hub for the grinding units improving theservice life of the grinding wheel to a certain extent. However, thesingle grinding unit is still operated at a zero rake angle during thegrinding process, so that the grinding efficiency and the surfacequality cannot be further improved. Meanwhile, the circumferentialspacing of the orderly arranged grinding units in the grinding processreaches 1 mm, which will result in a typical intermittent grinding, andthe generated periodic vibrations by the grinding process may alsoaffect the integrity of the processed surface.

Further, in order to improve the integrity of the processed surface andachieve the grinding in a positive rake angle, Chinese Publication No.105728961A, titled “Method for manufacturing a new positive-rake anglediamond grinding tool based on pulse laser”, provides a method forprocessing positive rake angles of diamond abrasive grains by laser. Inthe method, the large single-layer diamond abrasive grains orderlyarranged on the working surface of the grinding wheel are ablated bylaser to obtain a point angle less than 90°, which enables thepositive-rake angle grinding. The method effectively solves the problemthat abrasive grains of the conventional diamond grinding wheel cut thesurface of the workpiece in a large negative rake angle, which improvesthe processing efficiency and reduces the damage to the processedsurface, improving the integrity of the processed surface. However, inthe process of processing large-sized diamond abrasive grains by laser,the high laser ablation temperature will inevitably cause partialgraphitization on the diamond abrasive grains, affecting thepositive-rake angle cutting of the abrasive grains for the workpiecesurface and reducing the surface quality of the processed surface. Atthe same time, the single large-sized diamond abrasive grain may falloff if it is subjected to excessive or concentrated force, which mayaffect the grinding efficiency and even reduce the service life of thegrinding wheel.

In order to further improve the quality of the processed surface and thegrinding efficiency, Chinese Publication No. 107243848A, titled “Aspiral ordered fiber tool for positive rake angle processing andpreparation method thereof”, discloses a method in which the matrix isprepared on the grinding wheel hub by pressing and sintering, and theordered holes are processed on the matrix using a drilling bit. Then thefiber with positive rake angle is consolidated in the small holes by theepoxy resin. The method enables the positive-rake angle cutting, andfurther improves the surface quality and the processing precision.However, since the fiber has a cross-sectional size of 0.8 mm×0.8 mm andthe number of fibers per square centimeter on the surface of the tool isonly 14.26, the single fiber may have a large cutting depth, making itdifficult to ensure the processing precision. Moreover, a rupture willoccur if a single fiber is subjected to an excessive or concentratedforce, which may affect the service life of the grinding wheel. Thereare also great difficulties in the process that all the fibers areinserted into the small holes one by one and consolidated.

SUMMARY OF THE INVENTION

This application provides an orderly-micro-grooved PCD grinding wheelfor positive rake angle processing and a preparation method thereof toovercome the defects in the prior art.

The orderly-micro-grooved PCD grinding wheel produced herein comprises apolycrystalline diamond film (PCD film), a wheel hub, a plurality ofmicrogrooves and a plurality of micro-grinding units, wherein the PCDfilm is deposited on an outer circumferential surface of the wheel hub;the microgrooves, which has an axial length that is equal to a thicknessof the grinding wheel, a circumferential width of 20-50 μm, a depth of500-800 μm and a depth-width ratio of 10-40:1, are provided on an outercircumferential surface of the PCD film; individual micro-grinding unitswith a positive rake angle is provided between two adjacentmicrogrooves; and the microgrooves and the micro-grinding units arerespectively arranged in an ordered manner. In addition, themicrogrooves and the micro-grinding units are connected as a whole bythe PCD film, which can greatly improve the holding force of thegrinding wheel on the micro-grinding units to prevent the micro-grindingunits from singly falling off due to excessive or concentrated grindingforce, extending the service life of the grinding wheel. At the sametime, the ordered arrangement of the micro-grinding units with thepositive rake angle and the microgrooves with a high depth-width ratioon the working surface of the grinding wheel can reduce the grindingforce ratio, increase the chip-removing capacity and improve thechip-holding space, which effectively promotes the entering of thegrinding fluid into the grinding zone to significantly improve thecooling effect for the grinding zone, reducing thermal damage to thegrinding zone and effectively enhancing the grinding quality.

This application further provides a method for manufacturing the abovePCD grinding wheel, comprising:

1) mechanically producing a wheel hub of a grinding wheel;

depositing a PCD film with a thickness of 1-2 mm on an outercircumferential surface of the wheel hub by a hot filament chemicalvapor deposition technique (HFCVD);

2) polishing an outer circumferential surface of the diamond film by ionbeam polishing to obtain a surface roughness of the PCD film of 0.15-0.2μm;

3) processing the outer circumferential surface of the PCD film bywater-jet guided laser preparation technique: focusing a laser beamemitted by a laser head in a nozzle through a glass window on a waterchamber; pressurizing the water chamber to allow a water jet to beejected from the nozzle and to guide the transmission of the laser beamto the outer circumferential surface of the PCD film; offsetting thegrinding wheel by a certain angle, and producing a single microgroovewith an axial length that is equal to the thickness of the grindingwheel, a circumferential width of 20-50 μm, a depth of 500-800 μm and adepth-width ratio of 10-40:1 according to a relative movement orbit ofthe water jet and the wheel hub; indexing the grinding wheel, androtating an outer circumference of the PCD film through acircumferential width of one micro-grinding unit to carry out theprocessing of the next microgroove, wherein the micro-grinding unit witha positive rake angle is formed between the two adjacent microgrooves;and processing the micro-grinding unit to form a clearance angle;

4) repeating step (3) to form a plurality of microgrooves with highdepth-width ratio and a plurality of ordered micro-grinding units withthe positive rake angle at the entire circumference of the PCD film;wherein respective micro-grinding units are the same in size; and

5) subjecting the product prepared in step (4) to pickling and thenultrasonic cleaning in deionized water to form the orderly-micro-groovedPCD grinding wheel for positive rake angle processing.

The wheel hub is made of titanium alloy, and has a diameter of 100-200mm and a thickness of 6-20 mm.

Respective micro-grinding units have an axial length that is equal tothe thickness of the grinding wheel, a circumferential width of 80-150μm, a radial height of 500-800 μm and a circumferential spacing of100-200 μm.

In step (3), the micro-grinding units formed by processing the PCD filmwith the laser beam have the positive rake angle of 10°-40° and theclearance angle of 20°-50°.

A laser device used in the water-jet guided laser technique is an Nd:YAGpulse laser which has a wavelength of 532 nm and a focused spot diameterof 30-100 μm.

A pressure of the water chamber used in the water-jet guided lasertechnique is 2-4 MPa, and a diameter of the water jet is 20-50 μm.

Compared to the prior art, this application has the following beneficialeffects.

(1) This application significantly improves the grinding performance andefficiency.

The outer circumferential working surface of the grinding wheel isprovided with a large number of micro-grinding units with a positiverake angle, which ensures that the micro-grinding units are worked in apositive rake angle during the grinding process, lowering the grindingforce ratio and temperature, effectively reducing the damage to thesurface and greatly improving the grinding performance and efficiency.

(2) This application significantly increases the chip-holding space andthe chip-removing.

A large number of microgrooves with high depth-width ratio are providedon the outer circumferential working surface of the grinding wheel,which greatly improves the chip-holding space. Meanwhile themicro-grinding units are orderly arranged so that ordered chip-removingchannels are formed during the grinding process, which greatly improvesthe chip-removing capacity and makes the grinding wheel less prone toblockage, effectively promoting the entering of the grinding fluid intothe grinding area, significantly improving the cooling effect for thegrinding zone, reducing the thermal damage to the workpiece surface andfurther enhancing the grinding quality.

(3) This application effectively avoids the graphitization of themicro-grinding units and greatly extends the service life of thegrinding wheel.

When the micro-grinding units are processed by the water-jet guidedlaser technique, a laser beam is focused in a nozzle through a glasswindow on a water chamber. Then the water chamber is pressurized toallow a water jet to be ejected from the nozzle and to guide the laserbeam, where the laser beam propagates along the water jet in a totalreflection in the water jet. During the processing, the laser is guidedby the water jet to the surface of the PCD film to ablate the PCD film,and the ablated PCD film is carried away by the water jet. Additionally,the water jet also cools the surface of the PCD film, which effectivelyprevents the graphitization of the micro-grinding units, providingbetter grinding performance and greatly enhancing the surface quality.

(4) This application significantly extends the service life of thegrinding wheel.

The PCD film on the outer circumferential surface of the grinding wheelprepared by a HFCVD technique is operated as a whole, and eachmicro-grinding unit is part thereof, which greatly improves the holdingforce of the grinding wheel on the micro-grinding units, preventing themicro-grinding units from singly falling off due to excessive orconcentrated grinding force and significantly improving the service lifeof the grinding wheel.

(5) This application increases the number of effective cutting edges andalleviates the periodic vibration during the grinding.

The microgrooves obtained by the water-jet guided laser technique have acircumferential width of only 20 μm, and the micro-grinding units have acircumferential spacing of only 100 μm, so that the number ofmicro-grinding units involved in grinding per unit area is significantlyincreased, greatly alleviating the periodic vibration during thegrinding. The micro-grinding units prepared by the method have thecharacteristics of high protrusion and good consistency, so that thecutting edge of each micro-grinding unit can participate in thegrinding, which greatly increases the number of effective cutting edgesin the grinding process and reduces the cutting depth of the singlecutting edge, effectively improving the grinding precision andefficiency.

(6) This application has simple preparation process and low cost.

The size and shape of the micro-grinding units on the outercircumferential surface of the grinding wheel both have a goodperiodicity. Therefore, in the preparation process, the relative motionrelationship between the Laser-Microjet device and the grinding wheelcan be controlled by the numerical control technology, which greatlyreduces the difficulty in preparation of the grinding wheel and lowersthe cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional view showing a grinding wheel hub afterdeposited with a polycrystalline diamond film on the outercircumferential surface.

FIG. 2 schematically shows the processing of a microgroove by water-jetguided laser technique.

FIG. 3 is a schematic diagram showing the grinding wheel provided withmicrogrooves on the outer circumference and a partially enlarged viewthereof.

FIG. 4 is a schematic diagram showing the processing of a workpiece witha grinding wheel and a partially enlarged view showing a contact zonebetween the grinding wheel and the workpiece.

In the drawings:

1—wheel hub; 2—PCD film; 3—laser head; 4—glass window; 5—water chamber;6—nozzle; 7—laser beam; 8—water jet; 9—micro-grinding unit;10—microgroove; 11—positive rake angle; 12—workpiece; and 13—clearanceangle.

DETAILED DESCRIPTION OF EMBODIMENTS

This application will be further illustrated with reference to theembodiments and drawings.

Referring to FIGS. 1-4, an orderly-micro-grooved PCD grinding wheel forpositive rake angle processing includes a wheel hub 1, a PCD film 2, aplurality of micro-grinding units 9 with a positive rake angle 11 and aplurality of microgrooves 10 with a high depth-width ratio. The PCD film2 with a thickness of 1-2 mm is deposited on an outer circumferentialsurface of the wheel hub 1. The microgrooves 10 which have an axiallength that is equal to a thickness of the grinding wheel, acircumferential width of 20-50 μm, a depth of 500-800 μm and adepth-width ratio of 10-40:1 are provided on the outer circumferentialsurface of the PCD film 2. The micro-grinding unit 9 with the positiverake angle 11 is provided between two adjacent microgrooves 10, and themicrogrooves 10 and the micro-grinding units 9 are both orderlyarranged. When the grinding wheel is configured to grind a workpiece 12,the micro-grinding unit 9 is in contact with the workpiece 12 in thepositive rake angle 11, which ensures that the micro-grinding unit 9 canbe used to process the workpiece in a positive rake angle 11. Themicrogrooves 10 are mainly configured to hold chip and store grindingliquid. The micro-grinding units 9 with a positive rake angle 11 canprocess the workpiece in a positive rake angle, which reduces thegrinding force ratio and the grinding temperature, effectively reducingthe surface damage and greatly improving the grinding performance andefficiency.

The orderly-micro-grooved PCD grinding wheel for positive rake angleprocessing is manufactured as follows.

Step (1)

A wheel hub 1 was mechanically prepared from titanium alloy, and had adiameter of 100 mm and a thickness of 12 mm. A PCD film 2 with athickness of 2 mm was deposited on an outer circumferential surface ofthe wheel hub 1 made of titanium alloy by a HFCVD technique, then theouter circumferential surface of the PCD film 2 was polished by ion beampolishing to obtain a surface roughness of the PCD film of 0.2 μm. Theprepared PCD film 2 was used as a whole, which facilitated thecombination with the wheel hub 1, so that the prepared PCD film 2 canbear greater grinding force, and was less prone to falling off,improving the service life of the grinding wheel.

Step (2)

The outer circumferential surface of the PCD film 2 was processed bywater-jet guided laser technique, where a laser beam 7 emitted by alaser head 3 was focused in a nozzle 6 through a glass window 4 on awater chamber 5. The water chamber 5 was pressurized to allow a waterjet 8 to be ejected from the nozzle 6 and to guide the transmission ofthe laser beam 7 to the outer circumferential surface of the PCD film 2.The grinding wheel was offset by a certain angle, and a singlemicrogroove 10 with an axial length (12 mm) that is equal to thethickness of the grinding wheel, a circumferential width of 20 μm, adepth of 500 μm and a depth-width ratio of 25 was manufactured bychanging the relative movement orbit of the water jet 8 and the wheelhub 1. Then the grinding wheel was indexed, and the outer circumferenceof the PCD film 2 was rotated over 100 μm, i.e., the circumferentialwidth of a micro-grinding unit 9, to carry out the processing for thenext microgroove 10. The micro-grinding unit 9 with a positive rakeangle of 30° was formed between the two microgrooves 10. Then themicro-grinding unit 9 was processed to form a clearance angle 13 of 40°.The micro-grinding unit 9 was configured to cut a workpiece in apositive rake angle during the grinding process, which reduced thegrinding force ratio and the grinding temperature, effectively reducingthe occurrence of surface micro-crack and greatly improving the grindingperformance and efficiency. Meanwhile, the water-jet guided lasertechnique can effectively prevent the micro-grinding unit 9 from beinggraphitized, so that the micro-grinding unit 9 can provide bettersurface-cutting effect, greatly extending the service life of thegrinding wheel and improving the surface quality.

Step (3)

Step (2) was repeated to form a plurality of microgrooves 10 with highdepth-width ratio and a plurality of ordered micro-grinding units 9 witha positive rake angle 11 at the entire circumference of the PCD film 2,and respective micro-grinding units 9 were the same in size. The orderedarrangement of the microgrooves 10 and the micro-grinding units 9greatly improved the chip-holding space and facilitated the formation ofordered chip-removing channels during the grinding process, so that thechip-removing capacity was improved, which made the grinding wheel lessprone to blockage. Moreover, the grinding fluid was promoted to enterinto the grinding zone to provide an improved cooling effect, reducingsurface thermal damage and effectively improving the grinding qualityand surface-processing precision. Meanwhile, respective micro-grindingunits were identical in geometry and size, so that the number ofmicro-grinding units involved in grinding per unit area wassignificantly increased during the grinding process, and the cuttingedge of each micro-grinding unit can participate in the grinding, whichgreatly increased the effective number of cutting edges and reduced thecutting depth of the single cutting edge, effectively improving thegrinding precision and efficiency.

Step (4)

The prepared grinding wheel was subjected to pickling and thenultrasonic cleaning in deionized water for 15 min to form theorderly-micro-grooved PCD grinding wheel for positive rake angleprocessing.

It should be understood that the above embodiments are only illustrativeof the invention and are not intended to limit the invention. Inaddition, various equivalent modifications and changes made by thoseskilled in the art without departing from the spirit of the inventionfall within the scope of the invention defined by the appended claims.

What is claimed is:
 1. An orderly-micro-grooved PCD grinding wheel forpositive rake angle processing, comprising: a wheel hub; a PCD film; aplurality of micro-grinding units with a positive rake angle; and aplurality of microgrooves; wherein the PCD film with a thickness of 1-2mm is deposited on an outer circumferential surface of the wheel hub;the microgrooves are provided on an outer circumferential surface of thePCD film, wherein each of the microgrooves has an axial length that isequal to a thickness of the grinding wheel, a circumferential width of20-50 μm, a depth of 500-800 μm and a depth-width ratio of 10-40:1;respective micro-grinding units with the positive rake angle areprovided between two adjacent microgrooves, and the microgrooves and themicro-grinding units are respectively arranged in an ordered manner;when the grinding wheel is configured to grind a workpiece, respectivemicro-grinding units are in contact with the workpiece in the positiverake angle to achieve positive rake angle processing; and themicrogrooves are mainly configured to hold chips and store a liquid. 2.The PCD grinding wheel of claim 1, wherein the wheel hub is made oftitanium alloy, and has a diameter of 100-200 mm and a thickness of 6-20mm.
 3. The PCD grinding wheel of claim 1, wherein respectivemicro-grinding units have an axial length that is equal to the thicknessof the grinding wheel, a circumferential width of 80-150 μm, a radialheight of 500-800 μm and a circumferential spacing of 100-200 μm.
 4. Amethod of manufacturing the PCD grinding wheel of claim 1,comprising: 1) depositing the PCD film with a thickness of 1-2 mm on theouter circumferential surface of the wheel hub by a HFCVD technique; 2)polishing the outer circumferential surface of the PCD film by ion beampolishing to obtain a surface roughness of the PCD film of 0.15-0.2 μm;3) processing the outer circumferential surface of the PCD film bywater-jet guided laser preparation technology: and focusing a laser beamemitted by a laser head in a nozzle through a glass window on a waterchamber; pressurizing the water chamber to allow a water jet to beejected from the nozzle and to guide the transmission of the laser beamto the outer circumferential surface of the PCD film; offsetting thegrinding wheel by a certain angle, and producing one microgroove with anaxial length that is equal to the thickness of the grinding wheel, acircumferential width of 20-50 μm, a depth of 500-800 μm and adepth-width ratio of 10-40:1 according to a relative movement orbit ofthe water jet and the wheel hub; indexing the grinding wheel, androtating an outer circumference of the PCD film through acircumferential width of one micro-grinding unit to carry out theprocessing of the next microgroove, wherein the micro-grinding unit witha positive rake angle is formed between the two microgrooves; andprocessing the micro-grinding unit to form a clearance angle; 4)repeating step (3) to form a plurality of microgrooves with highdepth-width ratio and a plurality of ordered micro-grinding units withthe positive rake angle at the entire circumference of the PCD film;wherein respective micro-grinding units are the same in size; and 5)subjecting the product prepared in step (4) to pickling and thenultrasonic cleaning in deionized water to produce theorderly-micro-grooved PCD grinding wheel for positive rake angleprocessing.
 5. The method of claim 4, wherein the wheel hub is made oftitanium alloy, and has a diameter of 100-200 mm and a thickness of 6-20mm.
 6. The method of claim 4, wherein respective micro-grinding unitshave an axial length that is equal to the thickness of the grindingwheel, a circumferential width of 80-150 μm, a radial height of 500-800μm and a circumferential spacing of 100-200 μm.
 7. The method of claim4, wherein in step (3), the micro-grinding units formed by processingthe PCD film with the laser beam have the positive rake angle of 10°-40°and the clearance angle of 20°-50°.
 8. The method of claim 4, wherein instep (3), a laser device used in the water-jet guided laser technique isan Nd:YAG pulse laser, and the Nd:YAG pulse laser has a wavelength of532 nm and a focused spot diameter of 30-100 μm.
 9. The method of claim4, wherein in step (3), a pressure of the water chamber used in thewater-jet guided laser technique is 2-4 MPa, and a diameter of the waterjet is 20-50 μm.